1. Field of the Invention
This invention relates to a zoom lens with an anamorphic converter. In particular, the invention relates to a small, light weight zoom lens for a television camera or other camera that requires a high zoom ratio and a large aperture. An anamorphic converter that differs in the magnification in the vertical direction and the horizontal direction is freely attachable and detachable in order to selectively use the conversion of the length-breadth ratio of the image.
2. Background of Related Art
Conventionally, zoom lenses with a large aperture and high zoom ratio have a four-group construction. Lens groups are generally arranged in order from the object side having a positive--negative--negative--positive or positive--negative--positive--positive refractive power arrangement. Also, during zooming from the maximum wide-angle state to the maximum telephoto state, the second lens group and the third lens group move along the optical axis.
Moreover, conventionally, there have been various proposals for a converter that may be detachably installed either to the object side or the image side of the zoom lens. The attachment changes the length-breadth ratio of the image.
In recent years, while zoom lenses have had a large aperture, wide image angle, and a wide zoom ratio, there has been increased demand for a high performance zoom lens that is small and light weight. In general, while maintaining or decreasing the size and lightening the weight of the zoom lens, the method of strengthening the refractive power of each lens group is used, in order to achieve the required high specifications of the zoom lens. However, simply strengthening the refractive power of each lens group causes a decrease in image formation performance and sacrifices the correction of various aberrations.
Also, for television cameras, it is required that the zoom lens side (including converters) corresponds to the conversion and such of the aspect ratio. The correspondence improves performance and allows decrease in size of the solid television camera component by means of technological development.
In addition, the converter is installed so as to be attachable to and detachable from the image side and the object side of the zoom lens. Even with the conventional system listed above that records images and changes the length-breadth ratio of the image, the large size of the zoom lens system is inconvenient.